Dieter Ströhl

Martin Luther University Halle-Wittenberg | MLU · Institute of Chemistry

Acid hydrolysis of stevioside resulted in a 63% yield of isosteviol (1), which served as a starting material for the preparation of numerous amides. These compounds were tested for cytotoxic activity, employing a panel of human tumor cell lines, and almost all amides were found to be non-cytotoxic. Only the combination of isosteviol, a (homo)-piper...

Albeit platanic acid has been known since 1956, its potential to act as a valuable starting material for the synthesis of cytotoxic agents has been neglected for many years. Hereby we describe the synthesis of a small library of amides and oximes derived from 3- O -acetyl-platanic acid, and the results of their screening as cytotoxic agents for sev...

Citation: Li, C.; Hilgeroth, P.; Hasan, N.; Ströhl, D.; Kressler, J.; Binder, W.H. Comparing C2=O and C2=S Barbiturates: Different Hydrogen-Bonding Patterns of Thiobarbiturates in Solution and the Solid State. Int. J. Mol. Sci. 2021, 22, 12679. https:// Abstract: Carbonyl-centered hydrogen bonds with various strength and geometries are often exploi...

Amides derived from platanic acid (30-nor-lupane skeleton) were converted in two steps into 21-aza-17,19-ethano-19-nor-urs-20-en-21-ium chlorides. These ursane-skeleton iminium salts are first in their class, and some of them proved as selective inhibitors of the enzyme butyrylcholinesterase while holding no inhibitory activity for acetylcholineste...

Due to their special chemical structure, tetraether lipids (TEL) represent essential elements of archaeal membranes, providing these organisms with extraordinary properties. Here we describe the characterization of a newly isolated structural element of the main lipids. The TEL fragment GDNT‐β‐Glu was isolated from Sulfolobus metallicus and charact...

Reaction of 3-O-acetyl-oleanolic acid (3) with formic acid/hydrogen peroxide at 100 °C for several hours provides an extraordinary but simple pathway to a taraxeran-28,14 β -olide type triterpenoid while the same reaction at 0 °C occurred without re-arrangement of the carbon skeleton, and an oleanane-28,13 β -olide was obtained instead. The product...

Gypsogenin (1) and hederagenin (2) were isolated by extracting the powdered roots of Saponaria officinalis and the pericarp of Sapindus saponaria, respectively. While the gypsophila derived saponin can be obtained easily and in large quantities as a technical product, the plant material from Sapindus saponaria is difficult to obtain in Europe and t...

Background: Resistance developments against established antibiotics are an emerging problem for antibacterial therapies. Novel antibiotics are urgently needed. Materials & methods: We developed novel small-molecule antibacterials which are easily accessible in a simple one-pot synthesis. The central cyclopentaindole core is substituted with two ind...

The reactions of phenylglyoxylic acids during the synthesis and biological evaluation of fungal metabolites led to the discovery of hitherto unknown compounds with a p-quinone methide (p-QM) structure. The formation of these p-QMs using 13C-labelled starting materials revealed a key-step of this reaction being a retro-Friedel–Crafts alkylation.

Isocyanide-based multicomponent reactions - especially the standard four component Ugi reaction - provide an easy and powerful access to compounds with an auspicious pharmacological potential. Therefore, a set of 16 novel derivatives of the diterpene dehydroabietylamine was synthesized by the Ugi-4CR. The subsequent screening of the synthesized α-a...

1,3-Diketo-cyclohexanes are part of approximately 790.000 structures, but compound 2 is the first example of an E ring annelated triterpenoid carrying a 1,3-diketo moiety in an additional ring. This compound was obtained starting from methyl platanoate (1) by epimerization at position C-19 of the triterpenoid skeleton followed by an intramolecular...

Parent pentacyclic triterpenoic acids such as ursolic-, oleanolic, glycyrrhetinic, betulinic and boswellic acid were converted into their acetylated piperazinyl amides that were coupled with rhodamine B. SRB assays to evaluate their cytotoxicity showed all of these triterpene-homopiperazinyl-rhodamine adducts 16-20 being highly cytotoxic for a pane...

The achievement of self-healing (SH) at ambient conditions (low temperature, no external input of energy) still presents a significant area of research, strongly linked to fast and efficient cross-linking reactions. We here investigate fast cross-linking reactions of star-shaped polymers containing copper chelating moieties (picolinazide) at the en...

The aggregation state of the α-sulfinyl-functionalized methyllithium compound [Li2{CH2S(O)Ph}2(TMEDA)2] (1) in solution and its carbenoid reactivity is presented. Temperature dependent NMR measurements of 1 in THF-d8 revealed the presence of an intermolecular dynamic process (dimer-monomer-dimer equilibrium) with a Gibbs free energy of activation o...

Heterotelechelic poly(n-butyl acrylate)s (PnBuA) bearing two different and complementing supramolecular groups (namely, barbiturate (Ba) and the Hamilton wedge (HW)) at their α-end and ω-end (Ba–PnBuA–HW) were prepared by a combination of the reversible addition–fragmentation chain transfer (RAFT) process and the thio–bromo click reaction. The succ...

A straightforward synthesis for the anticoagulant rodenticide chlorophacinone is described. The short synthesis uses commercially available mandelic acid and 1,3-indanedione as staring materials

A straightforward chiral pool synthesis for a non-natural calystegin, 3-epi-B2, is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs' catalyst-mediated ring closure metathesis reaction. Compared to calystegin B2, the target compound is no longer an inhibitor for a β -...

Methyl glycyrrhetinate was esterified at position C3 of ring A using different amino acids. A short, unbranched chain of four carbon atoms with two amino groups in positions 2 and 4 was shown to be the most active compound of this series (IC50 = 0.8 M on liposarcoma Lipo cells). These compounds trigger apoptosis as shown by an acridine orange/ethid...

The pentacyclic triterpene glycyrrhetinic acid is an interesting natural product exhibiting various biological activities. Especially its ability to induce apoptosis in tumor cells is of high scientific interest. In this study we altered the lipophilicity in ring A by derivatization at positions C-2 and C-3. The consequences of these variations on...

A previously unknown dimer of the well-established analgesic flupirtine has been found, and its structure was revealed by ESI-MS, NMR spectroscopy and an independent synthesis. Thus, starting from 2-amino-6-chloro-3-nitro-pyridine the target compound was obtained in a four-step synthesis. Key-step of this synthesis is a nickel-mediated aryl-aryl co...

The dinuclear platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) reacted with 2-pyridyl-functionalized monoximes and with dioximes in the presence of NaOMe to yield oxime–diacetyl platinum(II) complexes [Pt(COMe)2(2-pyCR═NOH)] (R = H, 4a; Me, 4b; Ph, 4c) and [Pt(COMe)2(HON═CR–CR═NOH)] (R/R = Me/Me, 5a; Ph/Ph, 5b; (CH2)4, 5c; NH2/NH2, 5d), respectively....

Novel polyhydroxylated (E)-stilbenes were synthesized by Mizoroki-Heck reactions and tested for their ability to inhibit the enzymes acetyl- and butyrylcholinesterase. Several of them are good inhibitors of butyrylcholinesterase; one of them carrying an extra fluorine substituent is a 94-fold stronger inhibitor of butyrylcholinesterase than of acet...

A previously unknown dimer of the well-established analgesic flupirtine has been found, and its structure was revealed by ESI-MS, NMR spectroscopy and an independent synthesis. Thus, starting from 2-amino-6-chloro-3-nitro-pyridine the target compound was obtained in a four-step synthesis. Key-step of this synthesis is a nickel-mediated aryl-aryl co...

The extracts of the roots of licorice have been used in traditional and folk medicine to treat a broad variety of maladies. The main ingredient of these extracts is glycyrrhicinic acid. Its aglycon, glycyrrhetinic acid, has many biological activities, among them a pronounced cytotoxicity against tumor cells. In this study we varied glycyrrhetinic a...

Arglabin derivatives varied at the endo- or exo-cyclic double bond were synthesized and studied in a colorimetric sulforhodamine B assay for their cytotoxicity. Variations on the endocyclic double bond led to compounds of reduced cytotoxicity whereas derivatives from the reaction of the α-methylene-γ-butyrolactone moiety led to compounds of similar...

Several triterpenoic acids display a remarkable cytotoxicity on tumor cells. Glycyrrhetinic acid - the main content of the licorice root - possesses an apoptotic effect on tumor cells. Previous studies pointed out the presence of a keto group at position C-11 in glycyrrhetinic acid derivatives as the main reason for its apoptotic activity. Several...

Triterpenoic acids show many pharmacological effects, among them an antiinflammatory or an antitumor activity. One of these, glycyrrhetinic acid (1) is of interest because of its antitumor profile. Glycyrrhetinic acid is not only cytotoxic but also triggers apoptosis in various human tumor cell lines. To improve the cytotoxicity of parent 1 we set...

Glycyrrhetinic acid (GA) is a major ingredient of the dried extract of licorice roots; its antitumor activity is low compared to other members of the triterpenoic family. For example, oleanolic acid, betulin or betulinic acid are more cytotoxic with a pronounced activity for tumor cells. GA, however, is easily to earn, cheap and shows apoptotic eff...

A straightforward synthesis of the title compound (VIII) is elaborated involving a ring closue metathesis as key reaction.

The Heck reaction of cyclohexene with 1-chloroalk-1-ynes ClC≡CR 1 (R = Ph a, c-Hex b, n-Bu c, n-Oct d) 1) using [Pd(OAc)2]/NaO2CH/[NEt3Bz]Cl as catalyst system (DMF, 25°C) affords 1,3-disubstituted 7-(prop-2-ynylidene)bicyclo[2.2.1]heptanes 2 as tandem products by reaction of cyclohexene and ClC≡CR in a ratio of 1:2. To a smaller extent, substitute...

During the addition of amines to maleylamino acids in general β-amino derivatives are formed. In order to change the reactivity within the vinylogous maleyl system we introduced the β-benzylester group into the starting compound N-(cis-β-carboxyacryloyl)-phenylalanine methylester 1. The obtained benzylester 2 is adding benzylamine in α-position yie...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Several novel betulin derivatives were prepared and evaluated for their antitumor activity. 3-O-acetylbetulinic aldehyde served as an ideal starting material for the synthesis of 28-acetylenic derivatives. These compounds were further transformed into pyrazoles and 1,2,3-triazoles. Also, the synthesis of 3-amino substituted butenolides was carried...

Selective monofluorination of the α-glycosidase inhibitor and antidiabetic agent miglitol at positions C(2') or C(6) creates competitive inhibitors of glycosidases. Introducing a fluorine substituent at position C(6) results in a reduced binding to the enzyme whereas fluorination at C(2') produces an inhibitor with an activity four times higher tha...

An endoperoxide was synthesized starting from 11-keto-beta-boswellic acid and screened for antitumor activity in a panel of 15 human cancer cell lines by an SRB assay. The compound induces apoptosis and shows an average IC(50) value of 0.4-4.5 microM.

Aminoalkyl substituted derivatives were synthesized starting from glycyrrhetinic acid methyl ester and screened for antitumor activity in a panel of 15 human cancer cell lines by an SRB assay. The most compound 7 possesses an aminohexyl side chain, induces apoptosis and shows IC50 values of 0.6-3.0 μM.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

By treating Cp2MCl2 (M = Ti, Zr) with magnesium in the presence of the diazadienes R1N = CR2CR2 = NR1 (R1 = R2 = Ph: 1a; R1 = Ph, R2 = Me: 1b) metallocene complexes of formula Cp2-Activated-M(R1NCR2 = CR2NR1) (M = Ti: 2a, b; M = Zr: 3a, b) have been obtained in good yields. 2a-3b exhibit dynamic NMR spectra indicating a rapid intramolecular migrati...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The reaction of betulinic aldehydes with various carbon nucleophiles gave a series of new betulin derivatives, among them epoxides, glycidic derivatives and beta-hydroxy carbonyl compounds. Subsequent transformations of the beta-hydroxy carbonyls lead to 1,3-diketo- and alpha,beta-unsaturated betulin derivatives. These compounds were assayed for cy...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Difluorination of 1-deoxynojirimycin at position C(3) creates a competitive inhibitor 15 of 10 times higher activity against an α-glucosidase than the parent compound. Its screening against a panel of human cell lines showed a low cytotoxicity therefore making this compound an interesting candidate for further clinical investigations.

The aryl C-13 chemical shifts of Cl-substituted 4-amino-, 4-diazonium-N,N-dimethylanilines, N,N-dimethylanilines and differently substituted naphthalenes were assigned by means of different NMR methods. The assignments were compared with chemical shifts obtained by using empirical additivity relationship for mono substituted aromatic substances. As...

Starting from substituted 9-chloroacridines, a series of quinacrine and spacered dimeric acridine compounds was prepared. Their ability to interrupt the protein association of prion- and Alzheimer-specific proteins and Ab peptides was explored using a fast screening system based on FACS analysis. The bis-acridines displayed a higher activity than t...

A series of triterpene endoperoxides was synthesized and screened for antitumor activity in a panel of 15 human cancer cell lines by a sulforhodamine-B (SRB) assay. The compounds induce apoptosis and show excellent antitumor activity.

The synthesis of dimeric compounds derived from quinazolin-2-one and 1,4-benzodiazepin-2-one possessing a piperazine or homopiperazine spacer was investigated. In addition, a piperazine spacered bis-isoalloxazine and a bis-riboflavin compound were prepared and their ability to interrupt the association of prion proteins and Alzheimer-specific Abeta...

N-epsilon-(Carboxymethyl)-L-lysine is easily obtained by reductive amination of glyoxylic acid with N-alpha-acetyl-L-lysine in the presence of a palladium catalyst and hydrogen.

The stability and reactivity of organocobaloximes containing fluorinated alkyl ligands proved to be strongly dependent on the position of fluorination, as shown by the synthesis of Ph3P−[Co]−CH2CH2CH2F and py*−[Co]−CH2CHF2 ([Co] = bis(dimethylglyoximato)cobalt, py* = py, 4-(t-Bu)py). In the 2-monofluorinated cyclohexyl and -pentyl complexes py*−[Co...

Durch Umsetzung des Aquabis(dimethylglyoximato)ethylrhodium(III)-Komplexes, H2O—[Rh]—Et (1) ([Rh] = Rh(dmgH)2; dmgH2 = Dimethylglyoxim), in methanolischer KOH mit zweizähnigen Liganden RnY—CH2—CH2—YRn (YRn = NH2, PPh2, PMe2, SMe) sowie mit 4, 4′-Bipyridin (4, 4′-bpy) im Molverhältnis 1:0.5 sind symmetrisch substituierte binukleare Ethylrhodoxime Et...

Hyaluronic acid (HA) is a linear polysaccharide formed from disaccharide units containing N-acetylglucosamine and glucuronic acid. When HA was digested with the enzyme hyaluronidase, a double bond is formed. It is known that this double bond forms a complex (radical scavenger) with the radicals (ROO, HO) during UV irradiation, and reduced the toxic...

Treatment of bis(4-methoxybenzylthio)acetylene (1) with iodine monochloride yields different products in the presence or absence of nucleophiles such as water or alcohols. Normally, the electrophilic cyclisation of bis(benzylthio)acetylenes produces 1H-2-benzothiopyrans 2 by intramolecular ortho attack on the aromatic ring by a vinyl cation formed...

Reactions of aquabis(dimethylglyoximato)ethylrhodium-(III), H 2O-[Rh]-Et (1) ([Rh] = Rh(dmgH)2; dmgH2 = dimethylglyoxime), in methanolic KOH with bidentate ligands R nY-CH2-CH2-YRn(YRn = NH2, PPh2, PMe2, SMe) as well as with 4,4′-bipyridine (4,4′-bpy) in molar ratio 1:0.5 resulted in formation of symmetrically substituted binuclear ethylrhodoximes...

The title compound was studied by H and C NMR in CD2Cl2 solution and by C CPMAS NMR and X-ray diffraction in the solid phase. Low-temperature NMR spectra showed separate signals for the two cyclohexyl rings, located E and Z with respect to . Distinct resonances of cyclohexyl carbons are also present in the solid state C NMR spectrum. The barrier to...

The monomeric complex [LiCH2SPh(pmdta)] (3; pmdta = N,N,N',N ",N "-pentamethyldiethylenetriamine), prepared by metalation of PhSCH3 with n-BuLi/pmdta, undergoes in toluene (room temperature, in daylight) extrusion of the methylene group with formation of [LiSPh(pmdta)] and CH4. In refluxing toluene this reaction is thermally induced and the dimeriz...

The Heck reaction of cyclohexene with 1-chloroalk-1-ynes ClC≡CR 1 (R = Ph a, c-Hex b, n-Bu c, n-Oct d) using [Pd(OAc)2]/NaO2CH/[NEt3Bz]Cl as catalyst system (DMF, 25 °C) affords 1,3-disubstituted 7-(prop-2-ynylidene)bicyclo[2.2.1]heptanes 2 as tandem products by reaction of cyclohexene and ClC≡CR in a ratio of 1:2. To a smaller extent, substituted...

[(PtMe(3)I)(4)] reacts with AgBF(4) in acetone to give fac-[PtMe(3)(Me(2)CO)(3)]BF(4) (2) which was isolated as strongly moisture and air sensitive, colorless crystals and characterized by microanalysis and NMR spectroscopy ((1)H, (13)C, (195)Pt). The X-ray structure analysis (orthorhombic, Pcab, a = 15.599(3) Å, b = 15.685(2) Å, c = 15.763(3) Å, Z...

The compound [Rh(Hdmg)2(PPh3)]– ([Rh]–), synthesized by reduction of [Rh]–Cl with NaBH4 in methanolic KOH, reacted with 1,2-disubstituted ethanes XCH2CH2X′ (X/X′ = Cl/OMe or Br/Br) forming [Rh]–CH2CH2OMe 1a as well as [Rh]–Br and ethylene as heterolytic fragmentation products. Heterolytic fragmentation of 1a enforced by protonation with acids (CF3S...

Cyclization reactions of α-ketohydrazonyl chlorides such as methyl 6-arylhydrazono-6-chloro-5-oxohexanoates (2) and the 6-arylhydrazono-6-chloro-5-oxohexanoic acids (3) with o-aminothiophenol lead to 1,4-benzothiazine derivatives. The tautomeric and isomeric equilibria are discussed using 1H and 15N NMR as well as X-Ray diffraction analysis.

The 1H, 13C and 15N NMR spectra of a series of polymethylene-bridged carbonylhydrazone bis(benzo-15-crown-5 ethers) 1–9 (n = 0−8) and bis(benzo-18-crown-6 ethers) 10–11 (n = 1,5) were recorded and assigned by COSY, HMQC and HMBC 2D NMR experiments. The stereoisomerism of the bridging RCHNNHC(O)(CH2)n moieties was studied by various useful NMR...

Chain elongated 2,4-diuloses 2, 4, 6, 9–11, 24, 25 were conveniently obtained from the corresponding aldonolactones 1, 3, 5 by their reaction with carbonyl compounds in the presence of sodium hydride. These hemiacetalic products can be transformed into C-glycosides by deoxygenation with Et3SiH/BF3·Et2O.

Substituted 3-anilino-1,5-diphenylpyrazoles1a–i were oxidized with Pb(OAc)4 in benzene or CH2Cl2 solution. The ESR measurements confirmed the formation of aminyl radicals3f–i frompara-CH3 substituted pyrazoles1f–i. The radical intermediates from unsubstituted pyrazoles1a–e were assigned to triarylaminium cation radicals These were generated by cons...

Various monocyclic 1,2-dithiines 6a,b,d-t were prepared via (Z,Z)-1,4-difunctionalized butadienes (4-11,19,20). A twisted cyclic structure A is unequivocally proved rather than of the ringopened valence isomer B. The reactivity of these 1,2-dithiines is described. Thermal as well as day-light induced sulfur extrusion is an important feature of thei...

The solution conformation of two cyclic-casomorphin-5 analogues H-Tyr-c(-d-Orn-Phe-Pro-Gly-)1 and H-Tyr-c(-Orn-Phe-Pro-Gly-)2 in DMSO-d 6 was studied by NMR spectroscopy and accompanying force field calculations. By especially employing1H,13C, and15N chemical shifts, respectively, the temperature coefficient of the amide proton chemical shifts,3 J...

The solution conformation of three linear tripeptides Boc-Ala-Val-Val-OMe1, Boc-Ala-Pro-Val-OMe2, and Boc-Ala-(D)Pro-Val-OMe3 was studied by NMR spectroscopy and accompanying force-field calculations. In one case,2, as preferred conformation the-turnall trans conformer was found.

The title compound 3, derived from (+)-camphor, allows preparatively useful conversions to be carried out at the 3,3′-bibornane skeleton. The reactions are characterized by steric factors. Despite the increasing steric strain in the bicyclic units, ring-closure reactions of 3 to born-2-ene anellated sulfur-heterocycles are possible, including the f...

3-exo,3′-exo-(1R,1′R)-bicamphor (12) is obtained from 3-exo,3′-exo-(1R,1′R)-bithtiocamphor (3) by condensation with hydrazine hydrate followed by hydrolysis of the resulting dihydropyridazine 11. Deprotonation of 12 with NaH and subsequent treatment with potassium hexacyanoferrate (III) furnishes the 2,2′-dioxo-3,3′-bibornanylidene 13, whilst reduc...

The oxidation of the leuco“ indigo precursors 1 affords, depending on the nature of the annulated heterocycle, 1,2-dithiines 2 or 12-membered cyclic bis-disulfides (dinners“) 3, respectively. An equilibrium can exist between 2 and 3 in solution which has been investigated by means of NMR and molecular modelling studies in one instance (X = O). 3 ha...

Crystal structures of N-phenyl-N'-propylthiourea and the complex of N,N-bis(4,4'-difluoro-2-biphenyl)urea with N,N,N',K-tetramethylurea have been determined by single-crystal X-ray diffraction. Both structures are stabilized by formation of intra- and intermolecular hydrogen bonds. The first compound adopts an anti-syn conformation whereas the seco...

New Syntheses of Methyleniminium Salts from Carbonyl Compounds and from α‐Chloro Ethers; an Access to Vinylogous Viehe Salts * Two methods for the synthesis of isolable methyleniminium salts and amidinium salts are presented. In the first case carbonyl compounds A are treated with a mixture of (dialkyl‐amino)trimethylsilane ( 12 ) and chlorotrimeth...

A computer program with many useful functions for the prediction and assignment of the C-13 NMR spectra Of substituted benzenes, naphthalenes, and biphenyls is described. Additionally, for benzenes and naphthalenes, the program proved useful in searching for the types of substituents and their positions on the rings of the studied aromatic compound...

Peptidyl methyl ketones are reversible inhibitors of serine and cysteine proteinases and can be employed as ligands in affinity chromatography. Serine proteinases of the subtilisin family may be purified using the tripeptidyl methyl ketone -Ala2PheCH3 as ligand, whereas for papain, the best-known cysteine proteinase, both the -Ala2PheCH3 and the...

13C NMR contact shifts induced by the 2,2,6,6,-tetramethylpiperidine nitroxide radical (TMPN) were measured for N,N-dimethyl-para-substituted benzamides and N,N-dimethyl-β-bromo- and -α,β-methylacrylamides. The shifts were linear functions of radical concentration, cr. It was found that N-methyl group anti to the carbonyl group is a better acceptor...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The aryl13C chemical shifts of Cl-substituted 4-amino-, 4-diazonium-N,N-dimethylanilines, N,N-dimethylanilines and differently substituted naphthalenes were assigned by means of different NMR methods. The assignments were compared with chemical shifts obtained by using empirical additivity relationship for mono substituted aromatic substances. As a...

The new substituted alkyl 3-hydroxy propene dithioates 2a-e, ketene dithioacetals 3a-e, and 1,3-thiazoline-2-ones 4a-c are prepared by dithiocarboxylation of the 6-substituted N-acceptormethyl ben-zothiazoline-2-ones 1a-f.The crystal structure of 4b derived from 1c by ring opening via nuleophilic attack of the intermediate enedithiolate on the ring...

During the addition of amines to maleylamino acids in general ß-amino derivatives are formed. In order to change the reactivity within the vinylogous maleyl system we introduced the ß-benzylester group into the starting compound N-(cis-ß-carboxyacryloyl)-phenylalanine methylester1. The obtained benzylester2 is adding benzylamine in a-position yield...

Conformational investigations of the tetrapeptide Pro-D-Phe-Pro-Gly in water solution were carried out by 1H and 13C NMR spectroscopy. The internal proline residue allows for the possibility of cis/trans isomerization about the D-Phe-Pro peptide bond resulting in two conformational isomers. The major isomer was identified as the trans isomer. The p...

Titanocene- and Zirconocene(diazadiene) Complexes: Preparation, Characterization, and Structure By treating Cp2MCl2 (M = Ti, Zr) with magnesium in the presence of the diazadienes R1N = CR2CR2 NR1 (R1 R2 Ph:1a; R1 Ph, R2 Me: 1b) metallocene complexes of formula Cp2) (M Ti: 2a, b; M Zr: 3a, b) have been obtained in good yields. 2a–3b exhibit dynamic...

 The Heck reaction between 1-chloro-2-phenylacetylene and cycloalkenes or cycloalkadienes affords phenylethynyl substituted cycloalkenes as regular Heck products as well as 1,3-diphenylprop-2-ynylidene and (cycloalkenyl)phenylmethylidene substituted bicyclic compounds as tandem products by reaction of ClC*CPh and the cycloalkene in a ratio of 1:2 a...